Prosoft-technology MVI69-MCM Manual de usuario descargar pdf (Pagina 115)

MVI69-MCM ♦ CompactLogix or MicroLogix Platform Reference

Modbus Communication Module User Manual

ProSoft Technology, Inc. Page 115 of 167

March 22, 2011

5.4 Normal Data Transfer

Normal data transfer includes the paging of the user data found in the module’s

internal database in registers 0 to 4999 and the status data. These data are

transferred through read (input image) and write (output image) blocks. The

following topics describe the structure and function of each block:

5.4.1 Block Request from the Processor to the Module

These blocks of data transfer information from the processor to the module. The

structure of the output image used to transfer this data is shown below:

Offset Description Length (words)

0 Write Block ID 1

1 to (n)

Write Data

(n)

(n) = 60, 120, or 240 depending on the Block Transfer Size parameter (refer to the configuration

file).

The Write Block ID is an index value used to determine the location in the

module’s database where the data will be placed.

5.4.2 Block Response from the Module to the Processor

These blocks of data transfer information from the module to the processor. The

structure of the input image used to transfer this data is shown below:

Offset Description Length (words)

0 Read Block ID 1

1 Write Block ID 1

2 to (n+1)

Read Data

(n)

(n) = 60, 120, or 240 depending on the Block Transfer Size parameter (refer to the configuration

file).

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Prosoft-technology MVI69-MCM Manual de usuario Pagina 115